implantable cardioverter defibrillator (ICD)

Introduction

Implantable device to automatically detect & terminate ventricular tachycardia or ventricular fibrillation by delivering or more shocks to the heart to terminate the arrhythmia.

Indications

• serious arrhythmias not controlled by medication*
  • hemodynamically significant ventricular arrhythmia
    • ventricular fibrillation, cardiac arrest
• risk of arrhythmia due to underlying heart disease#
  • cardiomyopathy with LVEF <= 35%
• NYHA class II or III heart failure +
  • predicted survival > 1 year +
  • ischemic cardiomyopathy > 40 days post MI or non-ischemic cardiomyopathy with LV ejection fraction <= 35% or
  • history of hemodynamically significant ventricular arrhythmia or cardiac arrest
  • candidates for left ventricular assist device or cardiac transplantation (out of hospital)
• ischemic cardiomyopathy with NYHA class I-III heart failure & LV ejection fraction <= 30%
• for class III or IV NYHA heart failure & ECG QRS duration > 120 msec, cardiac resynchronization therapy with defibrillator indicated
• hereditary predisposition to fatal arrhythmias
  • hypertrophic cardiomyopathy
• high-risk features for sudden death & LVEF < 45%
  • pulmonary sarcoidosis insufficienty high risk
• sustained ventricular arrhythmias (> 30 seconds)
• cardiac arrest without reversible etiology
• subcutaneous ICD recommended for patients with inadequate vascular access or high infection risk from an ICD, & for whom pacing is not required
• > 40 days since myocardial infarction or > 3 months since PCI or CABG (see Procedure: below)

* The multicenter automatic defibrillator implantation trial (MADIT) showed better survival in patients with inducible ventricular tachycardia with implanted defibrillators than those treated with anti-arrhythmic agents.

# ICD may benefit patients with history of myocardial infarction & low LV ejection fractions (< 30-35%) > 40 days after MI.

* may benefit younger patients (HR=0.65) but not older patients

# Life expectancy should be > 1 year

Contraindications

• patients with new onset heart failure*
• no survival benefit for patients with severe LV dysfunction
• no benefit for renal dialysis patients unless LVEF < 35%

* left ventricular function may recover

Procedure

• these devices may be installed without thoracotomy
• some devices have back-up bradycardia & anti-tachycardia pacing
• devices are installed in the cardiac catherization laboratory
• after electrode placement & testing, a small generator (circuitry, capacitor, battery) is place under the skin in the chest
• subcutaneous ICD (without pacemaker) FDA-approved Sept 2012
  • no differences in complications or mortality among patients with subcutaneous vs transvenous ICD
• the device records when arrhythmias occur & shocks are delivered
• battery life of 3-5 years
• shocks may occur during sinus rhythm or atrial fibrillation
• overall 1 year survival 90%
• dual-chamber ICDs are associated with significantly more implant complications & no improvement in outcomes relative to single-chamber devices
• placement should be delayed until 40 days post-MI or 3 months after percutaneous coronary intervention (PCI)
  • echocardiogram prior to ICD placement
  • ICD placement prior to hospital discharge if post MI ventricular tachycardia > 24 hours post MI
• routine defibrillation testing may increase complications without improving outcomes

Complications

• infection
  • originate in subcutaneous pocket created for generator box
  • etiologic agents
    • coagulase-negative Staphylococcus
    • Staphylococcus aureus
  • management:
    • removal of the generator box
      • do NOT aspirate device pocket
        • may damage leads or introduce infection
    • systemic antibiotics for 2 weeks
    • epicardial & transvenous wires
      • should also be removed if possible
      • if not, 6 weeks of antibiotic therapy
• device malfunction
  • inappropriate shocks increase mortality
  • women have fewer appropriate shocks and more lead complications
• electromagnetic interference
  • avoid metal detection devices at airports, courthouses ...
  • cell phones may be used, but it is prudent to keep cellphone on opposite side of body from ICD
  • avoid magnets or strong magnetic fields, i.e. MRI is contraindicated
    • MRI-conditional devices are those that that FDA has determined do not pose additional hazards under prespecified conditions
    • older ICDs (pre-2015) with asynchronous pacing capabilities (although not MRI-conditional devices) also generally safe with MRI
  • iphone 12 circular array of magnets around a central charging coil may interfere with function of ICD
  • common electromagnetic devices may interfere with operation of defibrillators
    • these include Apple iPhone 12, Apple AirPods Pro & their wireless charging case, Microsoft Surface Pen, & Apple Pencil 2nd generation
• failure to prevent sudden death
  • recurrent myocardial infarction & cardiac rupture account for 50% of deaths after myocardial infarction
• perforation of the ventricular wall by ICD lead causing pericarditis, pericardial effusion, hemopericardium, pleural effusions & hemothorax
• venous thrombosis, possibly superior vena cava syndrome
• 6.1 complications/100 patient-years follow-up
  • 2.6/100 require reoperation (generally device malfunction, infection)
  • risks higher with cardiac resynchronization therapy- defibrillator (CRT-D) devices vs single-chamber devices
• brief episodes of atrial tachyarrhythmia are not associated with increased risk for stroke or other cardiovascular events
• patients with chronic kidney disease & heart failure have greater risk of hospitalization for heart failure with than without ICD (17 vs 11/100 person years)
• inappropriate shock more likely in elderly with multiple corbidities (RR=2.1) when implanted for primary prevention

Management

• monitoring needed
• programming of ICDs to prevent inappropriate therapy for supraventricular tachycardia & nonsustained ventricular tachyarrhythmias:
  • reduces unnecessary shocks
  • improves survival
  • does not increase the frequency of syncope
• amiodarone effectively blocks many ICD shocks
• metal detectors (hand-held & gates) used at airports are "probably safe" for patients with cardiac pacemakers or implantable cardioverter-defibrillators (ICDs)
• many patients with ICDs can safely participate in vigorous sports
• surgery: perioperative management
  • shock therapy should be turned off
    • electrocautery during surgery cause the ICD to interpret the electrical activity as ventricular fibrillation & initiate a shock
  • pacing function should be change to asynchronous mode
    • the asynchronous mode allows the pacing to continue regardless of cardiac electrical activity or electrocautery
• end-of-life - do not resuscitate (DNR) order:
  • discuss with patient reasons for the DNR order
• see ICD driving guidelines

Notes

• 20% of implantable cardioverter-defibrillators are placed contrary to evidence-based guidelines
  • use of carvedilol rather than metoprolol associated with lower rate of inappropriate ICD placement
• < 10% of eligible older adults receive ICDs within 1 year after myocardial infarction
• implantable cardioverter-defibrillators (ICDs) & cardiac resynchronization therapy (CRT) devices often include a feature that measures intrathoracic impedance, potentially providing an early warning system for decompensation by detecting pulmonary fluid retention
• explanted ICDs can be reused safely to help people who otherwise would not be able to afford them
• may be covered by Medicare
• potential cybersecurity vulnerabilities with Medtronic's implantable cardioverter defibrillators (ICDs) & cardiac resynchronization therapy defibrillators (CRT-Ds)
  • wireless telemetry system used for communication does not use encryption, authentication, or authorization

More general terms

• cardiovascular implantable electronic device (CIED)
• defibrillator

More specific terms

• automatic implantable cardioverter/defibrillator (AICD)

Additional terms

• cardiac device infection
• cardiac pacemaker
• cardiac resynchronization therapy
• ICD driving guidelines
• multicenter automatic defibrillator implantation trial (MADIT)